I need to keep watch on how much bandwidth some connections are taking in a server, and I know I have seen a top-like tool for that before. However, I can't remember the name of the tool, and I'm not having much luck searching for it.

Ok, I'm really enjoying pktstat. I like iftop's display better, but seeing the URLs is particularly useful for me at the moment! I'll stick with my original accepted answer on the grounds that it provided a Windows alternative as well, and that iftop does the job.
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Daniel C. SobralJun 10 '11 at 18:29